#08.5 _ Some of Earth’s circumstances have been observed also on other planets

of the Solar System

Why do we study the other planets of our Solar System if not to better understand Earth’s complexity? Some of the circumstances that occurred to the primordial Earth have been also observed on other planets.

The volcanic magma from which Tharsis formed probably contained significant quantities of H2O, CO2 and SO2 that would have been released, providing gases to the atmosphere and possibly contributing to an early, thicker atmosphere. Tharsis volcanism may have supplied gases that helped maintain a climate conducive to weathering and erosion, and the cessation of volcanism may have allowed other processes to begin removal of much of the atmosphere.

Central Tharsis region on Mars A comparison of Earth’s and Mars’ atmospheres

Titan, or also called Saturn VI, is the largest moon of Saturn. It is the only natural satellite known to have a dense atmosphere and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found.

The thick organic haze that shrouds Titan is similar to Earth’s early atmosphere; this environment that might have helped the raise early life. Indeed, experiments that reproduced the atmosphere in the early Earth and Titan today produced considerable amounts of organic material, which could have been one of the ways life first appeared.

It has been argued that Martian water was delivered by asteroids and comets from beyond 2.5 AU. Also, it was suggested that Mars’ interior is dry because, although the planet acquired a late volatile-rich veneer, it did not get folded into the mantle. A dry mantle explains the early demise of plate tectonics on Mars. In contrast to the Earth and Venus, Mars lost its atmosphere to space by hydrodynamic escape during the first few hundred Myr after accretion. Fractionation of the atmospheric 38Ar/36Ar ratio attests to hydrodynamic escape.

Also, introduction of water into the terrestrial mantle triggered plate tectonics, which may have been crucial for the emergence of life. Although this mechanism seems to have failed for Mars, may have worked for the young Venus (Albarède, 2009).